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Title: Nanotechnology Application for Solar Cells: Using Quantum Dots to Modify Absorption Properties


1
Nanotechnology Application for Solar Cells
Using Quantum Dots to Modify Absorption
Properties
  • Prepared by
  • James Fodor
  • Kwok Mak
  • Viet Huynh

2
Introduction
  • How Classical Solar Cells Operate
  • Absorption Coefficient (a)
  • Definition and Relevance of a
  • Physical Techniques for Measuring a
  • Light Absorption of Quantum Dot Layers
  • Reasons for Interest Into Quantum Dot Light
    Absorption
  • Definition of a Quantum Dot
  • Formula for Light Absorption of a Quantum Dot
  • Comparison of a versus Energy for Bulk Material
    and Quantum Dot
  • Researchers working on Light Absorption of
    Quantum Dots
  • Dr. Sheila Baily
  • Dr. Ryne Raffaelle
  • Problem Statement Determining the most
    optically absorbent semiconductor material
  • Problem Solution
  • Explanation of Theory
  • Results

3
Introduction
  • How Classical Solar Cells Operate
  • Absorption Coefficient (a)
  • Definition and Relevance of a
  • Physical Techniques for Measuring a
  • Light Absorption of Quantum Dot Layers
  • Reasons for Interest Into Quantum Dot Light
    Absorption
  • Definition of a Quantum Dot
  • Formula for Light Absorption of a Quantum Dot
  • Comparison of a versus Energy for Bulk Material
    and Quantum Dot
  • Researchers working on Light Absorption of
    Quantum Dots
  • Dr. Ryne Raffaelle
  • Dr. Sheila Baily
  • Problem Statement Determining the most
    optically absorbent semiconductor material
  • Problem Solution
  • Explanation of Thoery
  • Results

4
How Classical Solar Cells Operate1,2
5
How Classical Solar Cells Operate1,2
6
How Classical Solar Cells Operate1,2
7
How Classical Solar Cells Operate1,2
8
How Classical Solar Cells Operate1,2
9
How Classical Solar Cells Operate1,2
10
How Classical Solar Cells Operate1,2
11
How Classical Solar Cells Operate1,2
12
Introduction
  • How Classical Solar Cells Operate
  • Absorption Coefficient (a)
  • Definition and Relevance of a
  • Physical Techniques for Measuring a
  • Light Absorption of Quantum Dot Layers
  • Reasons for Interest Into Quantum Dot Light
    Absorption
  • Definition of a Quantum Dot
  • Formula for Light Absorption of a Quantum Dot
  • Comparison of a versus Energy for Bulk Material
    and Quantum Dot
  • Researchers working on Light Absorption of
    Quantum Dots
  • Dr. Ryne Raffaelle
  • Dr. Sheila Baily
  • Problem Statement Determining the most
    optically absorbent semiconductor material
  • Problem Solution
  • Explanation of Thoery
  • Results

13
Absorption Coefficient a Definition and
Relevance of a3
  • Definition of Absorption Coefficient a
  • A measure of the rate in decrease of
    electromagnetic radiation (as light) as it passes
    through a given substance the fraction of
    incident radiant energy absorbed per unit mass or
    thickness of an absorber.

14
Absorption Coefficient a Definition and
Relevance of a3
  • Unit of Absorption Coefficient a
  • The units of a are per length (cm-1)

15
Absorption Coefficient a Definition and
Relevance of a3
  • Unit of Absorption Coefficient a
  • The units of a are per length (cm-1)

16
Absorption Coefficient a Definition and
Relevance of a4
  • Absorption Versus Transmission
  • Transmission (t) a measure of conduction of
    radiant energy through a medium, often expressed
    as a percentage of energy passing through an
    element or system relative to the amount that
    entered.

17
Absorption Coefficient a Definition and
Relevance of a4
  • Absorption Versus Transmission
  • Transmission (t) a measure of conduction of
    radiant energy through a medium, often expressed
    as a percentage of energy passing through an
    element or system relative to the amount that
    entered.

18
Absorption Coefficient a Definition and
Relevance of a4
  • Absorption Versus Transmission
  • Transmission (t) a measure of conduction of
    radiant energy through a medium, often expressed
    as a percentage of energy passing through an
    element or system relative to the amount that
    entered.

19
Absorption Coefficient a Physical Techniques
for Measuring a5,6
  • Optical Transmission Measurement
  • t Measured transmission
  • l Sample thickness
  • R - Reflectance

20
Introduction
  • How Classical Solar Cells Operate
  • Absorption Coefficient (a)
  • Definition and Relevance of a
  • Physical Techniques for Measuring a
  • Light Absorption of Quantum Dot Layers
  • Why We Are Interested
  • Definition of a Quantum Dot
  • Formula for Light Absorption of a Quantum Dot
  • Comparison of a versus Energy for Bulk Material
    and Quantum Dot
  • Researchers working on Nano-coating
  • Dr. Ryne Raffaelle
  • Dr. Sheila Baily
  • Problem Statement Determining the most
    optically absorbent semiconductor material
  • Problem Solution
  • Explanation of Theory
  • Results

21
Light Absorption of Quantum Dots Why We Are
Interested7,8,13
  • These structures have great potential for
    optoelectronic applications, one of which may be
    solar cells
  • Standard solar cells have a theoretical upper
    conversion rate of 33, the theoretical limit on
    the conversion of sunlight to electricity is 67

22
Light Absorption of Quantum Dots Definition of
a Quantum Dot9
  • Quantum Dot

23
Light Absorption of Quantum Dots Definition of
a Quantum Dot9
  • Quantum Dot Layer

24
Light Absorption of Quantum Dots Definition of
a Quantum Dot9
  • Quantum Dot Layer

25
Light Absorption of Quantum Dots Formula7
  • _
  • Vav Average Dot Volume
  • pfi 2d momentum matrix element
  • a polarization of light
  • N(??) density of states

26
Light Absorption of Quantum Dots Formula12
  • Transmission for Quantum dots.
  • For transmission through n planes of dots, each
    having the same dot density N and each dot
    experiencing the same optical field amplitude,
    the transmission fraction is
  • Tn(1-sN)n (1-nsN) (sN ltlt 1)
  • s represents a cross section of the layer

27
Light Absorption of Quantum Dots Comparison of
a versus Energy for Bulk Material and Quantum Dot9
28
Light Absorption of Quantum Dots Comparison of
a versus Energy for Bulk Material and Quantum Dot
29
Light Absorption of Quantum Dots Comparison of
a versus Energy for Bulk Material and Quantum Dot
30
Light Absorption of Quantum Dots Comparison of
a versus Energy for Bulk Material and Quantum Dot7
31
Light Absorption of Quantum Dots Comparison of
a versus Energy for Bulk Material and Quantum Dot7
32
Introduction
  • How Classical Solar Cells Operate
  • Absorption Coefficient (a)
  • Definition and Relevance of a
  • Physical Techniques for Measuring a
  • Light Absorption of Quantum Dot Layers
  • Reasons for Interest Into Quantum Dot Light
    Absorption
  • Definition of a Quantum Dot
  • Formula for Light Absorption of a Quantum Dot
  • Comparison of a versus Energy for Bulk Material
    and Quantum Dot
  • Researchers working on Light Absorption of
    Quantum Dots
  • Dr. Ryne Raffaelle
  • Dr. Sheila Baily
  • Problem Statement Determining the most
    optically absorbent semiconductor material
  • Problem Solution
  • Explanation of Theory
  • Results

33
Researchers Working on Light Absorption of
Quantum Dot Layers
  • Dr. Sheila Bailey
  • Using quantum dots in a solar cell to create an
    intermediate band
  • IEEE Photovoltaic Specialist Conference (PVSC)
    Executive Committee since 1987

http//www.grc.nasa.gov/WWW/RT2001/5000/5410bailey
1.html
34
Researchers Working on Light Absorption of
Quantum Dot Layers11
  • Dr. Ryne Raffaelle
  • Rochester Institute of Technology
  • NanoPower Laboratories
  • Organic and Plastic Solar Cells Combined with
    Quantum Dot Layers

http//www.physlink.com/News/Images/QDots1_lg.jpg
35
Introduction
  • How Classical Solar Cells Operate
  • Absorption Coefficient (a)
  • Definition and Relevance of a
  • Physical Techniques for Measuring a
  • Light Absorption of Quantum Dot Layers
  • Reasons for Interest Into Quantum Dot Light
    Absorption
  • Definition of a Quantum Dot
  • Formula for Light Absorption of a Quantum Dot
  • Comparison of a versus Energy for Bulk Material
    and Quantum Dot
  • Researchers working on Light Absorption of
    Quantum Dots
  • Dr. Ryne Raffaelle
  • Dr. Sheila Baily
  • Problem Statement Determining the most
    optically absorbent semiconductor material
  • Problem Solution
  • Explanation of Theory
  • Results

36
Problem Solution Explanation of theory
Photon Absorption
  • z propagation direction
  • nr refractive index
  • omega frequency
  • alpha absorption coefficient
  • Laws of Conservation
  • Energy
  • Momentum

Photon Emission
Figures based on Singh textbook
37
Problem Statement Determining the most
optically absorbent semiconductor bulk
  • Consider InP and GaAs as being the available
    semiconductors to create a solar cell. This
    solar cell will be a hybrid, consisting of a
    traditional solar cell created with either InP or
    GaAs, and coating layers of quantum dots of
    either InP or GaAs. If maximizing absorption is
    the only criteria for designing the solar cell,
    which material should be used for the bulk?
    Which should be used for the quantum dot layers?
    Assume the density of states for quantum dot
    layers of both materials is equal and occurs at
    the same point, E .1eV, and that the
    polarization-momentum product sum is the same in
    both cases.

38
Problem Statement Determining the most
optically absorbent semiconductor bulk
  • Absorption coefficient of InP and GaAs
  • Required constants by material14

39
Introduction
  • How Classical Solar Cells Operate
  • Absorption Coefficient (a)
  • Definition and Relevance of a
  • Physical Techniques for Measuring a
  • Light Absorption of Quantum Dot Layers
  • Reasons for Interest Into Quantum Dot Light
    Absorption
  • Definition of a Quantum Dot
  • Formula for Light Absorption of a Quantum Dot
  • Comparison of a versus Energy for Bulk Material
    and Quantum Dot
  • Researchers working on Light Absorption of
    Quantum Dots
  • Dr. Ryne Raffaelle
  • Dr. Sheila Baily
  • Problem Statement Determining the most
    optically absorbent semiconductor material
  • Problem Solution
  • Explanation of Theory
  • Results

40
Problem Solution Results GaAs Bulk
41
Problem Solution Results InP Bulk
42
Problem Solution Results
43
Problem Solution Results GaAs Quantum Dot
Layer
44
Problem Solution Results InP Quantum Dot
Layer
45
Conclusion
  • How Classical Solar Cells Operate
  • Absorption Coefficient (a)
  • Definition and Relevance of a
  • Physical Techniques for Measuring a
  • Light Absorption of Quantum Dots
  • Reasons for Interest Into Quantum Dot Light
    Absorption
  • Definition of a Quantum Dot
  • Formula for Light Absorption of a Quantum Dot
  • Comparison of a versus Energy for Bulk Material
    and Quantum Dot
  • Researchers working on Light Absorption of
    Quantum Dots
  • Dr. Ryne Raffaelle
  • Dr. Sheila Baily
  • Problem Statement Determining the most
    optically absorbent semiconductor material
  • Problem Solution
  • Explanation of Theory
  • Results

46
References
  • Seale, Eric. Solar Cells Shedding a Little
    Light on Photovoltaics. 28, Feb. 2002.
    Solarbotics. lthttp//www.solarbotics.net/starting/
    200202_solar_cells/200202_solar_cell_physics.htmlgt
    . Accessed 03/20/2005.
  • Pierret, Robert F. Semiconductor Device
    Fundaments. Addison Wesley Longman, 1996. pp
    198-205.
  • Anonymous. Absorption Coefficient. Undated.
    LaborLawTalk. lthttp//dictionary.laborlawtalk.com/
    absorption_coefficientgt. Accessed 04/01/2005.
  • Anonymous. Transmission (T). Undated.
    Photonics Directory. lthttp//www.photonics.com/dic
    tionary/lookup/XQ/ASP/url.lookup/entrynum.5189/let
    ter.t/pu./QX/lookup.htmgt. Accessed 04/01/2005.
  • Augustine, G.  Jokerst, N.M.  Rohatgi, A.
    Absorption measurements of doped thin film InP
    for solar cell modeling. IEEE Indium Phosphide
    and Related Materials, 1992., Fourth
    International Conference on. 21-24 April 1992.
  • Gerber, D.S.   Maracas, G.N.  A simple method
    for extraction of multiple quantum well
    absorption coefficient from reflectance and
    transmittance measurements. Quantum Electronics,
    IEEE Journal of. Volume 29 , Issue 10. Oct.
    1993.
  • Kochman, B Singh, J et al. Absorption, Carrier
    Lifetime, and Gain in InAs-GaAs Quantum Dot
    Infrared Photodetectors. IEEE Journal of Quantum
    Electronics. Volume 39, Number 3. March 2003.
  • Anonymous. Photovoltaics. Evident Technologies.
    Undated. lthttp//www.evidenttech.com/applications
    /quantum-dot-solar-cells.phpgt. Accessed
    04/14/2005.
  • Singh, J. Modern Physics for Engineers. John
    Wiley Sons, Inc. 1999. pp 34, 156.
  • Wu, Y. Singh, J. Polar Heterostructure for
    Multifunction Devices Theoretical Studies.
    IEEE Transaction on Electron Devices. VOL. 52,
    NO. 2, FEBRUARY 2005
  • Raffaelle, R. Profile of Ryne P. Raffaelle. RIT
    Department of Physics. Undated.
    lthttp//www.rit.edu/physics/facstaff/profiles/raf
    faeller.shtmlgt. Accessed 04/10/2005.
  • Blood, P. On the Dimensionality of Optical
    Absorption, Gain, and Recombination in
    Quantum-Confined Structures. IEEE Journal of
    Quantum Electronics. Vol. 36, No. 3, March 2000.
  • D. Pan, E. Towne, and S. Kennerly. Strong
    normal-incident infrared absorption and
    photo-current spectra from highly uniform
    (In,Ga)As/GaAs quantum dot structures. IEEE
    Electronic Letters. 14th May 1998 Vol. 34 No.
    10.
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